1. Field of the Invention
The present invention relates to a method and apparatus for punching sheet material, and more specifically to a stripper insert component utilized during the sheet punching operation.
2. The Prior Art
In the manufacture of sheet material having punched openings, the sheet material is positioned on a lower die shoe for support in alignment with a vertically reciprocal punching tool. A vertically moveable die pad is generally interposed between the reciprocal punch and the lower die shoe and includes a bore therethrough to accommodate the vertical movement of the punch, the pad serving to engage, flatten, and stabilize the sheet material during the punching operation.
It has also been found desireable to utilize a so-called stripper insert positioned in the pad bore. The insert generally includes an opening therethrough to closely receive the punching tool, serving to further flatten the sheet material locally of the punched region. Further, the insert holds the sheet material against the lower die shoe while the punch is retracted, to eliminate the formation of a burr around the periphery of the punched opening.
Various types of stripper inserts have been used in punching operations, one such insert including a thick metal body for engaging and stabilizing the sheet material. This insert, however, has several inherent disadvantages. For example, the insert bore must be accurately machined and then the insert must be rather precisely positioned in mating alignment with the reciprocal punch. Further, if an irregular shaped insert bore is required because of the punch configuration, the insert must be cut in half for milling operations and then welded back together for placement in the punching die.
The present invention overcomes these and other disadvantages through a novel insert that can be secured in position on the punching die and then punched by the reciprocal punching tool to form the desired insert bore configuration.